Generate code from the unit definitions as part of the build

[tmilnthorp]

Problem

Building the solution compiled CodeGen but never ran it. After editing a JSON file in Common/UnitDefinitions, you had to remember generate-code.bat (or .sh), otherwise the build silently used stale generated code. CI ran CodeGen in a separate step, so local builds and CI could produce different results.

Change

• CodeGen runs itself after it builds (AfterTargets="Build" in CodeGen.csproj). UnitsNet has a build-order only reference to CodeGen (ReferenceOutputAssembly="false"), and every other project with generated code references UnitsNet, so they all build after the code is regenerated. No per-project opt-in is needed.
  • CodeGen runs once per build, and only when the unit definitions or CodeGen changed (MSBuild inputs/outputs), so a no-op build skips it.
  • Projects with a GeneratedCode folder pick up files that CodeGen added or removed in the same build, such as a new quantity (Directory.Build.targets).
  • It's skipped in IDE design-time builds, or with -p:SkipUnitsNetCodeGen=true.
  • Restore follows the reference, so building a single project (like the net48 job does) or UnitsNet.Modular.slnx works without CodeGen in the solution. --no-build doesn't build references, so pack and test with --no-build don't run it.
  • The reference doesn't show up as a package dependency.
• CodeGen only writes files whose contents changed, so regenerating doesn't touch timestamps or trigger rebuilds needlessly.
• CI no longer runs CodeGen as a separate step. Instead build.ps1 fails on CI if the build changed any generated files, meaning the committed generated code was out of date.
• generate-code.bat and generate-code.sh are removed, and the docs say to build instead. dotnet run --project CodeGen still works for regenerating without building.

Contributor workflow becomes: edit the JSON, then dotnet build (or build in the IDE).

Testing

• Editing Length.json and building regenerates the code; reverting and building restores it.
• A new quantity JSON compiles into UnitsNet.dll in the first build.
• A second build with no changes skips CodeGen.
• A clean solution build produces no changes to the committed generated code.
• The CI command shapes, with CodeGen not yet restored: a single test project build, pack --no-build, test --no-build, and the Modular restore + build --no-restore.

Not included

The header of generated files still says "generated by \generate-code.bat". It comes from the generator template, so changing it rewrites every generated file. I'd rather do that in a separate PR to keep this one reviewable.

🤖 Generated with Claude Code

https://claude.ai/code/session_012XKhDsyHDc5BHrmibxScqG

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98%. Comparing base (3bf1ef4) to head (92695b8).

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #1742   +/-   ##
======================================
  Coverage      98%     98%           
======================================
  Files         515     515           
  Lines       24092   24092           
======================================
  Hits        23692   23692           
  Misses        400     400           

Flag	Coverage Δ
net48	97% <ø> (ø)

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[tmilnthorp]

Related: #1745 proposes building on this so applications can generate their own quantities with the same CodeGen, as part of their own build, while still using the UnitsNet package.

🤖 Generated with Claude Code

https://claude.ai/code/session_012XKhDsyHDc5BHrmibxScqG